Effect of NaCrSi2O6 component on Lindsley’s pyroxene thermometer: An evaluation based on strongly metamorphosed LL chondrites

1Y. Nakamuta,2K. Urata,3Y. Shibata,4Y. Kuwahara
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12808]
1Kyushu University Museum, Kyushu University, Fukuoka, Japan
2Faculty of Science, Kyushu University, Fukuoka, Japan
3Sawara P.O., Japan Post Co., Fukuoka, Japan
4Graduate School of Social and Cultural Studies, Kyushu University, Fukuoka, Japan
Published by agreement with John Wiley & Sons

In Lindsley’s thermometry, a revised sequence of calculation of components is proposed for clinopyroxene, in which kosmochlor component is added. Temperatures obtained for the components calculated by the revised method are about 50 °C lower than those obtained for the components calculated by the Lindsley’s original method and agree well with temperatures obtained from orthopyroxenes. Ca-partitioning between clino- and orthopyroxenes is then thought to be equilibrated in types 5 to 7 ordinary chondrites. The temperatures for Tuxtuac (LL5), Dhurmsala (LL6), NWA 2092 (LL6/7), and Dho 011 (LL7) are 767–793°, 818–835°, 872–892°, and 917–936°C, respectively, suggesting that chondrites of higher petrographic types show higher equilibrium temperatures of pyroxenes. The regression equations which relate temperature and Wo and Fs contents in the temperature-contoured pyroxene quadrilateral of 1 atm of Lindsley (1983) are also determined by the least squares method. It is possible to reproduce temperatures with an error less than 20 °C (2SE) using the regression equations.

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